A chemical in cannabis can help ward off strokes and heart disease, scientists believe.

Swiss researchers found THC, one of 60 cannabinoids in the drug, helped stop the narrowing of arteries to the brain and heart in a study of mice.

But the team, from Geneva University Hospital, said smoking cannabis did not produce the same effect.

However UK experts warned more research was needed before firm conclusions could be drawn.

Deaths

Blocked arteries - a condition known as atherosclerosis - are estimated to be responsible for up to 50% stroke and heart disease deaths in developing countries each year.

In the study, published in the Nature journal, mice were fed a high cholesterol diet to make them develop atherosclerosis and then given THC, which causes the high during cannabis use.

The Swiss researchers found THC stopped inflammation of blood vessels, which is largely responsible for blocking arteries.

The chemical worked by suppressing the immune system's response to a protein which is responsible for inflammation.

We certainly hasten to advise against people smoking cannabis to protect their heart health

Professor Jeremy Pearson, of the British Heart Foundation

Lead researcher Francois Mach said while drugs such as statins which lower blood pressure and cholesterol had proved extremely effective the findings were still of "great medical interest".

And he added: "The dose [used] is lower than the dose usually associated with psychotropic effects of THC."

THC is being tested by GW Pharmaceuticals, the firm granted a UK licence to create cannabis-based drugs, in a number of treatments for pain relief and multiple sclerosis under development.

However, a study published last week in BMC Psychiatry found THC medicines could lead to psychosis.

Health

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, said more work needed to be done in the area.

"Although these results, which use an oral cannabinoid in a pill form, are interesting, we look forward to further research into the area.

"We certainly hasten to advise against people smoking cannabis to protect their heart health - cannabis is usually smoked with tobacco which is highly dangerous for the heart."

And a spokeswoman for the National Heart Forum said: "This study presents interesting findings about the protective effects of active components found in marijuana and suggests scope for further investigation of these compounds."

But she added: "It does not suggest that marijuana smoking is beneficial to the heart. On the contrary, the harmful effects on the heart are well documented."